We have developed a comprehensive program to help physicians advise smokers to quit. The program includes: 1) a seminar which will teach physicians about smoking cessation and use role-playing to improve their advice; and 2) a program of office-based counseling which identifies smokers by an intake questionnaire that asks about their smoking habits and smoking-related symptoms; individualized counseling from the physician about the benefits of quitting; a prescription from the physician for a date to quit; a booklet about quitting and instructions for physicians and patients in the appropriate use of nicotine gum. To minimize relapses, patients will make a one-month follow-up visit to reinforce their motivation to quit and learn skills to stay abstinent. To encourage physicians to continue to advise smokers, the program will include 1) "booster" conference calls between physicians and their seminar instructors, 2) a cumulative log of smokers who have accepted dates to quit and 3) postcards from patients who have successfully quit. We will undertake a randomized controlled trial to test the hypothesis that physicians who receive this program will achieve significantly higher long-term abstinence rates among their smoking patients than will those who do not receive the program. One hundred primary care physicians in private practice in San Francisco and 100 internists from six Kaiser-Permanente Medical Groups will be randomly allocated to receive the program or serve as controls. Twenty smokers randomly drawn from each physician's practice will be interviewed about their smoking habits 12 and 24 months after their entry into the study. We will measure expired carbon monoxide and saliva thiocyanate to verify abstinence. Our study has a power of at least .80 to detect a 5.6% difference in rates of abstinence between the experimental and control groups. We will also analyze the efficacy of the program in different subgroups of physicians and patient, identify predictors of physician efficacy in counseling and predictors of patients success in quitting and describe changes in physicians knowledge, attitude and behavior that result from the seminars. If the program is proven to be effective, it will be entirely applicable to other health care settings. It will also provide a basis for further study and analysis of the effectiveness of its individual components.